include/linux/bch.h

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  * Generic binary BCH encoding/decoding library
   4  *
   5  * Copyright © 2011 Parrot S.A.
   6  *
   7  * Author: Ivan Djelic <ivan.djelic@parrot.com>
   8  *
   9  * Description:
  10  *
  11  * This library provides runtime configurable encoding/decoding of binary
  12  * Bose-Chaudhuri-Hocquenghem (BCH) codes.
  13 */
  14 #ifndef _BCH_H
  15 #define _BCH_H
  16
  17 #include <linux/types.h>
  18
  19 /**
  20  * struct bch_control - BCH control structure
  21  * @m:          Galois field order
  22  * @n:          maximum codeword size in bits (= 2^m-1)
  23  * @t:          error correction capability in bits
  24  * @ecc_bits:   ecc exact size in bits, i.e. generator polynomial degree (<=m*t)
  25  * @ecc_bytes:  ecc max size (m*t bits) in bytes
  26  * @a_pow_tab:  Galois field GF(2^m) exponentiation lookup table
  27  * @a_log_tab:  Galois field GF(2^m) log lookup table
  28  * @mod8_tab:   remainder generator polynomial lookup tables
  29  * @ecc_buf:    ecc parity words buffer
  30  * @ecc_buf2:   ecc parity words buffer
  31  * @xi_tab:     GF(2^m) base for solving degree 2 polynomial roots
  32  * @syn:        syndrome buffer
  33  * @cache:      log-based polynomial representation buffer
  34  * @elp:        error locator polynomial
  35  * @poly_2t:    temporary polynomials of degree 2t
  36  * @swap_bits:  swap bits within data and syndrome bytes
  37  */
  38 struct bch_control {
  39         unsigned int    m;
  40         unsigned int    n;
  41         unsigned int    t;
  42         unsigned int    ecc_bits;
  43         unsigned int    ecc_bytes;
  44 /* private: */
  45         uint16_t       *a_pow_tab;
  46         uint16_t       *a_log_tab;
  47         uint32_t       *mod8_tab;
  48         uint32_t       *ecc_buf;
  49         uint32_t       *ecc_buf2;
  50         unsigned int   *xi_tab;
  51         unsigned int   *syn;
  52         int            *cache;
  53         struct gf_poly *elp;
  54         struct gf_poly *poly_2t[4];
  55         bool            swap_bits;
  56 };
  57
  58 struct bch_control *bch_init(int m, int t, unsigned int prim_poly,
  59                              bool swap_bits);
  60
  61 void bch_free(struct bch_control *bch);
  62
  63 void bch_encode(struct bch_control *bch, const uint8_t *data,
  64                 unsigned int len, uint8_t *ecc);
  65
  66 int bch_decode(struct bch_control *bch, const uint8_t *data, unsigned int len,
  67                const uint8_t *recv_ecc, const uint8_t *calc_ecc,
  68                const unsigned int *syn, unsigned int *errloc);
  69
  70 #endif /* _BCH_H */